Effect of clearance and inclined angle on sheared edge and tool failure in trimming of DP980 sheet

Ultra-high-strength steels are widely used in automotive industry for lightweight and high crash performance. In this study, the effects of process variables such as the clearance and the inclined angle of the die on the sheared edge characteristics of trimmed DP980 have been evaluated in detail. The maximum trimming load decreases with increasing clearance due to a large bending moment leading to a hydrostatic tensile stress in the sheared zone, and tensile typed burr occurs at a trimming clearance above 15.6%t. Also, a negative inclined angle improves the quality of sheared edge and decreases the trimming load. As a result of the trimming experiment, the burr height gradually increases with an increase in the number of strokes due to tool failure resulted from high contact pressure. Furthermore, the burr height significantly decreases as the localization zone is connected linearly from punch to die edge with the negative inclined angle.